Cathode ray tube with a grid of single continuous wire



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. HrT/zr J Fiance Hosea ay/4on0 CHHE N United States Patent Ofiice 9 Claims. in; 313-89) The present invention relates to cathode ray tubes. more particularly of the type comprising a grid placed in front of the screen and having dimensions comparable to those of the screen.

It is an object of the invention to provide an improved tube of the above type. this improvement being particularly, though not exclusively, suitable for tubes used in colour television and including a phosphor strip screen and a focusing grid.

In phosphor strip tubes, the beam or beams from one or more electronic guns generally reach the phosphor strips of the screen through a grid which is aimed at correctly focusing the electrons, where desired, while also post-accelerating them.

The grid wire elements building up the useful wire surface must be rigidly attached at their ends. be exactly parallel to each other and lie in the same plane.

It is an object of the invention to provide means for conveniently satisfying these requirements.

According to the invention, there is provided a grid comprising a frame. two parallel rods fixed to said frame, and a continuous wire extending from one rod to the other and forming between said rods a plane wire surface; each one of said rods comprising a longitudinal face, said face comprising substantially transversal parallel grooves, and thread elements separating said grooves; each of said thread elements terminating, at one end. in an overhanging portion; said continuous wire passing through at least some of said grooves of each of said rods, and. when two grooves through which it passes consecutively belong to the same rod, also passing under the overhanging portion or portions separating those two grooves.

The arrangement according to the invention has several advantages:

(:1) Since a single wire is used, all of the parallel grid wires are at the same potential.

(b) The grid wires are kept parallel to each other by the above mentioned grooves which may be readily formed with a great precision.

(c) The wire which forms the grid is readily wound manually or mechanically.

(cl) Both the guiding and anchoring of the wire are effected in a simple and yet effective manner by means of the thread.

According to a preferred embodiment of the rods according to the invention, the grooves are arcuate, each of them presenting a point such that the tangent thereto is parallel to said wire surface, each wire element leaving the groove through which it passes in the direction of said tangent.

According to a preferred embodiment of the invention, the frame of the grid is a rather light metal frame and is sealed along its periphery into the envelope of the tube, the strength of the frame necessary for tensioning the grid wire elements being mainly due to this sealing.

This makes it possible both to reduce the weight of the grid and to spread over a greater surface the stresses to which the tube may be submitted, due to the fact that the grid and screen assembly is attached thereto. This feature is particularly important where glass tube envelopes are concerned.

3,284,653 Patented Nov. 8, 19 56 invention will become apparent description and appended drawings Other features of the from the following wherein:

FIG. 1 is a horizontal sectional view illustrating very diagrammatically a colour television tube with a focusing grid, of a known type;

FIG. 2 is a perspective view of an embodiment of the grid frame for a grid according to the invention.

FIG. 3 is a sectional view of a detail view of FIG. 2;

FIG. 4 shows a preferred positioning of the grid frame of FIG. 2 in a tube according to the invention;

FIG. 5 illustrates a method of winding the wire on the frame of FIG. 2;

FIG. 6 is a view, on an enlarged scale, of a detail of FIG. 4;

FIG. 7 is a partial sectional view of a grid and screen assembly as secured in a tube; and

FIG. 8 is a partial sectional view of a tube, incorporating the grid and screen assembly of FIG. 7.

The same reference numbers were used throughout the whole of the specification to designate the same elements.

In FIG. 1, there is shown, very diagrammatically and in section, a colour television tube including three guns, a focusing grid and a phosphor strip screen. The tube envelope comprises a flared portion 1, which may be of glass, or of metal capable of being welded to glass, and the generally curved glass wall 2, peripherically scaled at 3. This envelope may have a circular or rectangular section.

Close to wall 2 is positioned a focusing grid 4 formed of wires and a screen 5 is positioned between wall 2 and grid 4. Screen 5 is formed of phosphor strips of the three primary colours, which may be for example red, green and blue.

In operation, grid 4 and screen 5 are brought to respective potentials Vg and Ve, by means of metal connections sealed in the envelope.

Three guns 6, 7 and 8 are located at the neck of the envelope. The electrons beams emitted by the guns converge at P, are focused and post-accelerated by grid 4 and impinge then upon screen 5, voltage Ve being generally much higher than voltage Vg. The beams are deflected by the deflector system, only a portion 9 of which is visible in the figure, so as to sweep the whole of the surface of screen 5.

This type of tube is known and is illustrated by way of example with a view towards showing how the invention improves the arrangement of the grid within the tube.

FIG. 2 shows in perspective the metal grid frame 10 for a tube according to the invention, having a rectangular section. This frame is formed with four holes 11 which serve for supporting screen 5.

This frame has a small thickness so that by itself it is not sufiiciently strong for correctly supporting the wires of the grids. Frame 10 has greater dimensions than those of the inner section, and preferably of the outer section, of the envelope into which it is built. The frame is made of a metal having an expansion coefficient matched to that of the glass of which the envelope is made.

Along the two large sides of the aperture of frame 10 are secured two rods 12, which are threaded with a pitch corresponding to the distance between the wires of the grid, and have been formed with ll ats along the bases fixed to the frame, as shown in FIG. 3.

Rods 12 are secured to the frame, for example, by means of screws 14 as shown in section in FIG. 3.

Due to the fact that another fiat forming the right hand face of the rod shown in FIG. 3 is not at right angles with the plane of the frame, overhanging projections 29 are formed, which projections serve for anchoring the wire elements extending across the aperture of the frame.

If the tube is entirely of glass, frame 10 can be secured to the periphery of the flared portion 1 thereof, for example by sealing it by means of enamel 16, as shown in section in FIG. 4, thus imparting thereto mechanical strength.

The sealing operation is effected by depositing, along the edge of the glass envelope, an enamel paste 16, the expansion coefficient of which matches that of glass and of the metal frame 10. The assembly is put into in an oven brought to a temperature such that the enamel is caused to fuse and thus ensures a correct sealing.

The assembly is then cooled and the wires can then be wound on frame 10 to form the grid.

If the operation of the tube is such that the grid potential may be the same as that of the flared portion, the latter may be built of metal and frame 10 may be soldered thereto, for example electrically.

In FIG. 4, it is noted that the ends of the wires 15 which build up the grid pass around the threads 29 of rod 12 and may be tensioned without any risk of distorting frame 10, since the latter is firmly built into envelope 1 and thus partakes in the strength of the latter.

FIG. 5, which is a drawing at a very enlarged scale,

shows the method of carrying out the winding, this operation being effected after sealing the frame onto the flared portion of the tube so that the frame should present a sufficient strength.

The grid is formed by a single continuous wire, which is wound around the lower portion of the teeth or overhanging thread ends 29.

In FIG, 5 only one rod 12 has been illustrated. Wire 15 is secured at one of its ends to a screw 17, runs along the bottom of the groove between the two first adjacent threads, is stretched across the aperture of frame 10, passes between the two first threads of the other rod 12, passes under the end of the adjacent thread, is returned to the first rod 12 to pass under the end of the adjacent thread and so on, as shown in FIG. 5.

The wires extending across the aperture of frame are thus kept parallel, due to the constant spacing between the threads, and the grid is flat because the points at which the wire leaves the grooves of each rod are respectively located along the two' parallel straight lines. When the winding of the grid is completed, the wire end is attached to another screw 17 (not illustrated). Screws 17 are threaded in the frame of the grid.

Rods 12 thus insure the attachment of the wires, keep them parallel and makes the obtained useful wire surface flat.

FIG. 6 is a fragmentary, sectional view of the tube, with the grid frame sealed into the flared portion of the tube envelope by means of an enamel coating 16. The figure shows the cross-section of the threaded rod 12, which is secured by a screw 14 to the frame 10 of the grid, and the wire 15 passing around the threads of rod 12. Preferably, as shown in FIG. 6, a coating of enamel 18 is deposited along the edge of the sharp end of rod 12 to seal the end of each wire element thereto and keep it attached to it, even if a temporary expansion occurs, for example during the vitrification of the enamel or the annealing of the enclosure.

The mounting of the grid-screen assembly is shown in FIG. 7. The phosphor screen 5, the phosphors of which are shown at 19, is secured on frame 23 by a plurality of blocks 24, for example four, and screws 25.

Frame 23 of the screen is fixed at a convenient distance from grid 15 by means of four rods 20 of an insulting material. Rods 20 are secured to the screen frame 23 and to the grid frame It) by means of crimped sockets 22 and 21. Socket 22 may be readily set into an ovally shaped recess of frame 23, so as to lock in positon the parallel grid wire elements with respect to the phosphor strips.

It is of course possible to substitute electric welding for screws, for example with a view towards avoiding any possible leakage of gases occluded between the screws and any cooperating member.

After the grid-screen assembly has been mounted on the flared portion 1 of the tube, the envelope may be closed by the dish shaped end portion 27 of the envelope, as shown in FIG. 8. This end portion is also sealed by means of an enamel coating 26, in the same manner as frame 10.

In the case of FIG. 8, the voltage Ve lead in is formed as a metal conductor 28, sealed into portion 27 of the tube.

The connection for applying voltage Vg to grid, shown in FIG. 1, may be made at that portion of frame 10 which is outside the envelope.

It is preferred that the outer perimeter of grid frame 10 should be greater than that of the flared portion 1 of the tube and of the end portion 27. This makes it possible to effect the enamel sealings, 16 and 26 under better conditions, even when the portions 1 and 27 do not have exactly the same section. The accepted margins in glass technics are such that incomplete juxtaposition may readily take place between portions 1 and 27, which would harmfully affect the mechanical resistance of the joints.

In the above description, several enamel sealings effected in succession have been mentioned. It is possible to make the sealing operations with enamel material of decreasing fusion temperature in the order of the manufacturing steps, or with the same type of enamel at a given fusion temperature, provided the crystalline structure reached at this temperature is maintained during the subsequent thermal operations.

Of course the above description is not limitative in particular, the rods 12 may have various sections, the essential feature being that the rod should have a grooved face, having a common edge with another face, which is so directed that the thread or projections separating the grooves from each other should have an overhanging terminal portion, which may be readily used for guiding and anchoring the grid wires.

Also, it may be desired for some particular application that the wire elements building up the grid should not be equidistant. In this case the grooves are not equidistant or, if they are, not all of them receive wire elements.

The grid may also be built with a frame having by itself a sufficient strength for supporting tensioned wire elements. The grid and screen assembly is in this case mounted within the tube in a conventional manner, for example by means of four spring leaves, which are laterally affixed to the four sides of the frame by one of their respective ends, the opposite ends having an aperture which is engaged by an element which is sealed to the envelope.

What is claimed is:

1. A grid comprising a frame, two parallel rods fixed to said frame, and a continuous wire extending from one rod to the other and forming between said rods a plane wire surface; each one of said rods comprising: a longitudinal face, said face comprising substantially transversal parallel grooves, and thread elements separating said grooves; each of said thread elements terminating, at one end, in an overhanging portion; said continuous wire passing through at least some of said grooves of each of said rods, and under at least some of said overhanging portions of said thread elements of each of said rods.

2. A grid comprising a plane frame, two parallel rods fixed to said frame, and a continuous wire; the lateral surface of each one of said rods comprising at least:

a longitudinal base portion resting on said frame;

a second longitudinal portion, including the top portion of said surface comprising substantially transversal arcuate grooves, and corresponding thread elements separating said grooves;

and a third longitudinal portion, adjacent to said second portion; said third portion being plane and not being at right angles with the plane of said frame, each of said thread elements thus terminating, on one side, in an overhanging portion; said continuous wire passing through said successive grooves of each of said rods and under alternate ones of said overhanging portions of said thread elements of each of said rods.

3. A grid as claimed in claim 2. wherein said continuous wire is sealed to said alternate ones of said overhanging portions.

4. A cathode ray-tube comprising an envelope, a screen and a grid parallel to said screen; said grid comprising a metal frame, two paralel rods, and a continuous wire; said frame comprising at least a portion peripherically sealed in said envelope, and an inner portion Within said envelope; said two parallel rods being fixed to said inner portion of said frame; the lateral surface of each one of said rods comprising at least a longitudinal portion resting on said frame;

a second longitudinal portion, including the top portion of said surface, and comprising substantially transversal parallel arcuate grooves, and corresponding thread elements separating said grooves;

and a third longitudinal portion, adjacent to said second portion; said third portion being plane and not being at right angles with the plane of said frame, each of said thread elements thus terminating, on one side, in an overhanging portion; said continuous wire passing through said grooves of each of said rods, and under alternate ones of said overhang ing portions of said thread elements of each of said rods, and being scaled to said alternate ones of said overhanging portions.

5. A cathode ray tube comprising an envelope, a screen and a grid parallel to said screen; said envelope comprising a dish shaped portion and a flared portion; said grid comprising a metal frame, two parallel rods, and a continuous wire; said frame having a portion peripherically scaled to said dish portion and to said flared portion, an inner portion within said envelope, and an outer portion projecting outward of said envelope; said rods being fixed to said inner portion of said frame; the lateral surface of each one of said rods comprising at least a longitudinal base portion resting on said frame;

a second longitudinal portion, including the top portion of said surface, and comprising substantially transversal parallel arcuate grooves, and corresponding thread elements separating said grooves;

and a third longitudinal portion, adjacent to said second portion; said third portion being plane and not being at right angles with the plane of said frame, each of said thread elements thus terminating, on one side, in an overhanging portion;

said continuous wire passing through said grooves of each of said rods, and under alternate ones of said overhanging portions of said thread elements of each of said rods and being scaled to said alternate ones of said overhanging portions.

6. A cathode ray tube as claimed in claim 5, wherein,

-said dish shaped portion and said flared portion being made of glass, said sealed portion of said frame is sealed with enamel to said dish shaped portion and to said flared portion.

7. A cathode ray tube as claimed in claim 5, wherein said dish shaped portion being made of glass and said flared portion being made of metal, said sealed portion of said frame is sealed with enamel to said dish shaped portion, and soldered to said flared portion.

8. A cathode ray tube comprising an envelope, a screen having phosphor strips, a grid, and means for maintaining said screen in parallel spaced relationship with said grid; said envelope comprising a dish shaped glass portion and a flared glass portion; said grid comprising a metal frame, two parallel rods and a continuous wire; said metal frame comprising an inner portion within said envelope, a portion sealed to said dish shaped portion and to said flared portion of said envelope, and an outer portion projecting outward of said envelope; said maintaining means and said rods being fixed to said inner portion of said frame; the lateral surface of each one of said rods comprising:

a longitudinal base portion resting on said frame;

a second longitudinal portion, including the top portion of said surface, and comprising substantially transversal parallel arcuate grooves, each of said grooves having a point where the tangent to said groove is substantially parallel to said strips, and corresponding thread elements separating said grooves;

and a third longitudinal portion, adjacent to said second portion; said third portion being plane and not being at right angles with the plane of said frame, each of said thread elements thus terminating, on one side, in an overhanging portion;

said continuous wire passing through said grooves of each of said rods, and under alternate ones of said overhanging portions of said thread elements of each of said rods and being sealed to said alternate ones of said overhanging portions.

9. An assembly for a cathode ray tube comprising: a screen with phosphor strips; a grid comprising a frame, two parallel rods fixed to said frame, a continuous wire, and means, fixed to said frame and to said screen for maintaining said grid and said screen in parallel spaced relationship, the lateral surface of each one of said rods comprising:

a longitudinal base portion resting on said frame;

a second longitudinal portion, including the top portion of said surface, and comprising substantially transversal arcuate grooves, each of said grooves having a tangent point where the tangent to said groove is substantially parallel to said strips, and corresponding thread elements, separating said grooves;

and a third longitudinal portion, adjacent to said second portion, said third portion being plane and not being at right angles with the plane of said frame, each of said thread elements thus terminating, on one side, in an overhanging portion;

said continuous wire passing through said grooves of each of said rods, and under alternate ones of said overhanging portions of said thread elements of each of said rods, and being sealed to said alternate ones of said overhanging portions.

References Cited by the Examiner UNITED STATES PATENTS 2,026,725 1/1936 Baker 313358 X 2,778,161 1/1957 Zaphiropoulos 49-81 2,897,392 7/1959 Fiore 313-92 2,936,391 5/1960 Curry et al. 313-348 2,957,140 10/1960 iHarris 313-89 X 3,069,586 12/1962 Antoniades 31389 X 3,112,421 11/1963 Raibourn et al. 313350 X JAMES W. LAWRENCE, Primary Examiner. R. SEGAL, Assistant Examiner. 

1. A GRID COMPRISING A FRAME, TWO PARALLEL RODS FIXED TO SAID FRAME, AND A CONTINUOUS WIRE EXTENDING FROM ONE ROD TO THE OTHER AND FORMING BETWEEN SAID RODS A PLANE WIRE SURFACE; EACH ONE OF SAID RODS COMPRISING: A LONGITUDINAL FACE, SAID FACE COMPRISING SUBSTANTIALLY TRANSVERSAL PARALLEL GROOVES, AND THREAD ELEMENTS SEPARATING SAID GROOVES; EACH OF SAID THREAD ELEMENTS TERMINATING, AT ONE END, IN AN OVERHANGING PORTION; SAID CONTINUOUS WIRE PASSING THROUGH AT LEAST SOME OF SAID GROOVES OF EACH OF SAID RODS, AND UNDER AT LEAST SOME OF SAID OVERHANGING PORTIONS OF SAID THREAD ELEMENTS OF EACH OF SAID RODS. 